Sliding door assemblies typically include a sliding door moveable between a closed position and an open position, a stationary door maintained in a stationary position, and a door frame surrounding and supporting the sliding door and the stationary door. A common problem with known sliding door assemblies is that they are not nearly as airtight and weatherproof as desired. While the stationary doors of such structures are readily securable weather tightly in their frames, the sliding doors pose a sealing problem which has long persisted.